The present invention relates to fluid jet machining and in particular to the use of fluid jets to machine to controlled depths in hard materials.
It is known to machine objects using high velocity water jets including an abrasive. In abrasive water jet systems a finely divided abrasive material is entrained in a high pressure jet of water which is directed at a component to be machined. Abrasive water jets are increasingly used in the manufacturing industries and have been successfully employed to cut relatively soft-materials to precise shapes. Difficulties have however been encountered in using water jets as a precision tool on harder materials due to difficulties in controlling the depth of cut.
In U.S. Pat. No. 5,704,824 an abrasive water jet is used to machine a component. The jet is attached to a manipulator which allows the jet to be moved in three dimensions. The apparatus allows for continuous variation in the position and strength of the jet as well as variations in the speed of relative motion between the jet and the component. A mask, of harder material, is positioned between the jet and the component and has an opening through which the jet is directed to machine the surface of the component. The mask is provided to define the area to be worked whist covering and thus protecting adjacent areas of the component.